My day begins with uncertainty. Will the rain hold off until this evening, as the weather forecast suggests? Or should I dash out to mow the lawn now in case it starts to drizzle this afternoon?

I boot up my computer to find a host of uncertainties confronting me. I read that U.S. stocks are starting the week in the red because of uncertainty over the Federal Reserve’s meeting this week. No one expects the Fed to do anything in terms of interest-rate policy, but one never knows what hyperbolic cues might be embedded in the statement released at the conclusion of the meeting on Wednesday.

When times are good — when stocks are soaring and economic growth is on a tear — no one talks about uncertainty.

That’s just a taste of the certain uncertainties. What about uncertain uncertainties, such as a terrorist attack or a coup in some foreign country? An out-of-nowhere event that could rattle financial markets? Perhaps some newly unearthed revelation will disqualify one of the U.S. presidential contenders. (OK, if Hillary Clinton’s shenanigans haven’t dented her front-runner status by now, maybe nothing will.)

Uncertain uncertainties — the equivalent of former Defense Secretary Donald Rumsfeld’s “unknown unknowns” — are a fact of life. So man up, you wusses!

It is axiomatic that markets hate uncertainty. That overused phrase has been around so long that it’s impossible to determine the source. Which is just as well since the whole idea is pretty silly.

Often uncertainty is a euphemism for pessimism. The financial crisis and Great Recession produced lots of uncertainty, according to everything I’ve read over the last eight years.

When times are good — when stocks are soaring and economic growth is on a tear — no one talks about uncertainty. The period leading up to the Nasdaq peak in March 2000 comes to mind. Many analysts warned of an internet- and tech-stock bubble, as first-time investors bought shares in companies that had no revenue, no profits and, in many cases, no viable business model. Misplaced optimism — it took 15 years for the Nasdaq to eclipse its 2000 high — is never labeled uncertainty.

Economists have a special relationship with uncertainty. It represents the antithesis of what policy makers hope to accomplish through clear communication. One of the guiding principles of today’s economics is something called the rational expectations hypothesis, the idea that outcomes depend on expectations. Among academics, REH is the equivalent of settled science and has been incorporated into econometric models.

The Fed and other central banks have signed on to REH, elevating talk — forward guidance is the polite name — to new levels based on the idea that the more markets know what to expect, the more effective policy will be.

Of course, few have stopped to question why such a good theory is being upended by reality. U.S. financial markets have consistently ignored the Fed’s projections for interest-rate increases during the current expansion. And it is the Fed that ultimately conforms to market expectations, not the other way around.

Every theory needs an index, so it was inevitable that a group of economists would develop something to reflect economic policy uncertainty. The graph of the U.S. economic policy uncertainty Index reveals no leading-indicator properties, ratcheting higher as it does during recessions and falling well after the recovery is underway.

Businesses large and small regularly complain about uncertainty. In most cases, the reference is to tax policy.

“Complain” is the operative word. Forget what they say. What do they do? Using data from the U.S. Census Bureau, a 2009 Kauffman Foundation study found that more than half the companies on the Fortune 500 list that year were started during a recession or a bear market.

“Recessions and bear markets, while they bring pain and often lead to short-term declines in business formation, do not appear to have a significantly negative impact on the formation and survival of new business,” according to the report.

Just think about that. Recessions produce tremendous policy uncertainty. The recommendation that fiscal stimulus be “timely, targeted and temporary” rarely satisfies all three conditions. And what about the transmission time from the implementation of policy to the outcome? Uncertain, if you ask me.

I hope I have convinced one or two readers of the flawed logic behind the uncertainty principle, not to be confused with a theory of the same name formulated by the late physicist Werner Heisenberg. Markets may hate uncertainty, but when is the future ever certain? Only death and taxes are absolutes. Everything else is up for grabs.

OK, I’ve said my piece. Now I can file this column, uncertain what my editor will think of it or what changes he’ll suggest. My day begins just where it began, in the land of uncertainty.

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